I also was an avid pre workout user and stopped using right away. It took maybe a week to readjust! I make almond butter/oat energy balls I’m place of it. Though know that you’ll be more tired in general and during workouts because you’re pregnant so give yourself grace - especially first trimester!
It was a rough time for me, but I eventually got used to just using a bit of black tea before my workouts!! My stash of pre looks at me every time I take my vitamins though and I’m like “ugh, it’s not for forever…” lol
You will be amazed at how quickly your body will adapt to NOT using it . I would use pre work out before every work out and once I stopped because of my pregnancy I was amazed at how much I could do with out it . Being a momma is like having superpowers haha I would drink a large coffee in the morning if I had the time but other than that just water